This invention relates generally to radio frequency (RF) transmitters and more particularly relates to RF transmitters capable of transmitting multiple codes at multiple frequencies.
Transmitters are becoming more and more widely used to control the operation of an ever increasing amount of devices and systems. Originally used for military applications and large-scale broadcasting needs, the transmitter has evolved to such an extent that it is now being used in applications as personal as medical implants. In fact it is becoming almost impossible to go without using a transmitter in our day-to-day lives. For example, our cars, garages, shutters, etc. may all be controlled via a transmitter.
Unfortunately, like all electronics, transmitters break, and become damaged and/or lost. When this happens, it often becomes necessary to purchase a new transmitter. Most manufacturers who sell products using transmitters offer replacement units for sale. In some industries, universal transmitters are offered for sale which can be used on a variety of products made by a variety of manufacturers. The garage door operator industry is one such industry.
In order to operate properly, universal movable barrier operator transmitters must be capable of transmitting a plurality of different codes (or code modulations) at a plurality of different frequencies (or carrier frequencies). These transmitters are sought after because consumers do not always know what type of transmitter they need, or they prefer having the security of knowing that they are getting a transmitter that will work with their system. Universal transmitters are also attractive to personnel who install and service movable barrier operators because they reduce the number of transmitters they need to stock and reduce the number of transmitters they need to learn how to program and/or operate. In addition, these transmitters can often times be sold for less than other replacement transmitters because the manufacturers can make up profit margins based on volume sales.
Unfortunately, in order to offer these capabilities, the electronic circuits comprising the transmitter become more complex, larger and expensive. For example, the addition of components can often create RF interference among the other components and/or require redesign of the circuit layout. Similarly, the added electronics often increase the size and expense of the circuit and may require the use of a larger, more expensive microprocessor or controller. Typically, only a portion of the larger controller is used which increases waste and lowers the efficiency of the overall circuit. This is because additional input and output (I/O) pins are required to handle the extra electronics required to produce multiple codes and frequencies.
To date, several attempts have been made to provide universal transmitters. One example is U.S. Pat. No. 5,564,101 to Eisfeld et al. which discloses a universal transmitter for use with a garage door opener which allows for a user to program a transmitted modulation format and carrier frequency and transmit a signal corresponding to the selections. This transmitter uses two sets of mechanical DIP switches to select the transmitter code and carrier frequency, but ties up individual I/O ports for each individual DIP switch. Such a configuration requires a larger controller having additional I/O ports, which will make the circuit more complex, increase the overall circuit size, and raise costs.
U.S. Pat. No. 5,661,804 to Dykema et al. discloses a learning transmitter which can operate a plurality of different receivers employing rolling or encrypted code. No user input is required to learn the code and frequency, other than activating the transmitter to be copied. A single RF circuit employing a phase locked loop frequency synthesizer and dynamically tunable antenna is provided for transmitting the learned code. Unfortunately, not all transmitters are functional when they are being replaced, so learning transmitters are not always available substitutes.
Accordingly, there is a need for a simple, smaller, and less expensive transmitter capable of transmitting a plurality of different codes at a plurality of different frequencies. There is also a need for a new way to connect multiple inputs and outputs to a controller so that less I/O ports are needed. There is a further need for a more efficient way of connecting and operating controllers or microprocessors.
An RF transmitter embodying the present invention provides a simple, compact and inexpensive circuit for transmitting a plurality of different codes at a plurality of different frequencies. The transmitter achieves this by connecting multiple inputs and/or outputs to a controller in a more efficient way so that fewer controller I/O ports are needed. More particularly, the RF transmitter continues to allow user-selection of code and frequency, but multiplexes the input to the controller so that multiple inputs can be coupled to a single controller input without losing the ability to determine the state of each input. In addition, the controller input can operate as both an input and output, thereby minimizing the need for additional I/O ports.
The RF transmitter comprises an input device for selecting among at least two different codes and bit patterns, and for transmitting the selected code and bit pattern at various frequencies as a receiver actuation signal. A three position switch allows the user to select the code the transmitter is to send, (i.e., manufacturer A""s code, B""s code, C""s code, etc.), and DIP switches allow the user to select the bit pattern to be transmitted. The transmitter can be provided with any number of button inputs for transmitting a selected code and frequency. Typically movable barrier operator transmitters are offered in one, two and four button models. While each transmitter is capable of transmitting a plurality of different codes at a plurality of different frequencies, the two and four button transmitters are capable of sending additional receiver actuating signals, (e.g., the four button transmitter can be used to open three separate garage doors and a gate without requiring the user to change the three position switches or the DIP switches on each transmission).
A controller is coupled to the input device and transmitter circuitry. Upon detection of a transmission command signal from a button input, the controller determines which button has been pressed, processes the code and bit pattern selections corresponding to that transmission command signal, and outputs a serial code signal responsive to these selections to the transmitter circuitry. Specifically, the controller determines what code and bit pattern has been selected and outputs the base band code signal to the transmitter circuitry associated with the selected data so that an appropriate receiver actuation signal will be transmitted at an appropriate frequency.
The controller has a plurality of I/O ports (or pins) and is coupled to the bit pattern input device in such a way that it is capable of determining the positions of multiple DIP switches through a single I/O pin. This configuration allows the transmitter to function with a less complicated controller, (i.e., a controller having fewer I/O ports). More particularly, the DIP switches are coupled to discrete logic components on one end and to the controller on the other. The controller I/O pins are pulled high through pull-up resistors and each I/O pin is connected to two DIP switches. One of the DIP switches is connected (on the other side) to ground through a capacitor, while the other is connected to ground through a pull-down resistor. Despite the fact the DIP switches are connected to the same I/O pin, the controller is capable of determining the position of each switch because the presence of the capacitor (or-lack thereof) will effect how the input on the I/O reacts. For example, if the switch connected to the pull-down resistor is closed and the switch connected to the capacitor is open, the I/O pin will be pulled low immediately. However, if both the switch connected to the pull-down resistor and the switch connected to the capacitor are closed, the I/O port will be pulled low slowly.
With such a configuration, four different states can be distinguished via one I/O pin, (thereby accounting for each position of the DIP switches), and the controller can operate much more efficiently. This does not only provide a more efficient controller I/O pin utilization, but it allows a single pin of the controller to be used as both an input and output. The addition of discrete components allows the controller to monitor time and voltage changes, and use each pin for multiple inputs.
Once the controller has processed the various inputs, it can output data responsive to the selected code and bit pattern to transmitter circuitry capable of transmitting an appropriate actuation signal. More particularly, when the processor has determined the various input states, it can output the selected code and bit pattern to transmitter circuitry capable of transmitting the information at the appropriate frequency. For example, if the user has selected code associated with manufacturer A""s equipment, has specified a particular bit pattern, and has depressed a transmission pushbutton, the controller will output the appropriate code and bit pattern to the transmitter circuitry that is set up to transmit this information at the frequency specified for manufacturer A""s products.